1. Field of the Invention
The present invention relates to a steering apparatus which includes a telescopic adjustment mechanism and an impact absorbing mechanism for absorbing impact in the event of a secondary collision, and in which these mechanisms can be shared by the same member, and moreover which can smoothly move from a telescopic adjustment region to an impact absorbing region when the steering apparatus contracts toward a front side in the event of a secondary collision.
2. Description of the Related Art
Conventionally, various steering apparatuses which include a telescopic adjustment mechanism and an impact absorbing mechanism for protecting a driver in the event of a secondary collision when a collision accident occurs are known. According to an example of a common structure of this type of steering apparatuses, a column moves along an axial slot while resisting against the pressing force of a bolt shaft in the event of a secondary collision.
Moreover, a type of steering apparatuses having a structure in which a width of an axial line is formed smaller than the diameter of a bolt shaft so that, when a predetermined load is applied, the column moves in a state in which the edge of the axial slot is collapsed by the bolt shaft is often used. An example of such a conventional technique as illustrated above is disclosed in Japanese Patent Application Laid-open No. 2002-337699. Hereinafter, Japanese Patent Application Laid-open No. 2002-337699 will be described briefly.
In this description, the reference numerals used in Japanese Patent Application Laid-open No. 2002-337699 are used as they are. However, in order to distinguish from the description of the present invention, the reference numerals are surrounded by parentheses in the description of Japanese Patent Application Laid-open No. 2002-337699. A steering apparatus disclosed in Japanese Patent Application Laid-open No. 2002-337699 has a second upper bracket (22) having an upper end welded to a column (2), and the second upper bracket (22) moves together with the column (2) in relation to a vehicle body when the column (2) moves in relation to the vehicle body due to an impact.
Moreover, the second upper bracket (22) is sandwiched between both side walls (21a and 21b) of a first upper bracket (21) fixed to the vehicle body so as to be slidable in relation to each other. Screw shafts (51) with heads (51′) having cores extending in a lateral direction are inserted into first through-holes (41) formed in both side walls (21a and 21b) of the first upper bracket (21) and second through-holes (42) formed in both side walls (22a and 22b) of the second upper bracket (22). The screw shaft (51) has a nut (54) that crews into the screw shaft (51) with a washer (52) interposed therebetween and a lever (53) that is integrated with the nut (54). A short diameter of an impact absorbing region (42) is set to be smaller than the largest outer diameter of the shaft (51) in a direction orthogonal to the relative moving direction. The shaft (51) presses and expands an impact absorbing region (42a) whereby the impact is absorbed.
Moreover, Japanese Patent Application Laid-open No. 2004-82758 discloses a conventional technique by which the amount of collision energy absorbed by an energy absorbing mechanism in the event of a secondary collision increases when collapse progresses. A guide hole (79) formed in an inner column (13) includes a telescopic portion (111) having such a vertical width that a guide pin (75) of a guide bolt (53) is loosely fit into the guide hole (79) and a collapsing portion (113) which extends rearward from the telescopic portion (111) and of which the vertical width decreases gradually.
A range in which the guide pin (75) moves in a front-rear direction inside the telescopic portion (111) is a telescopic stroke (S1) and a range in which the guide pin (75) retracts inside the collapsing portion (113) is a collapse stroke (S2). Since the vertical width of the collapsing portion (113) gradually decreases rearward, an impact absorbing load in the event of a secondary collision of a driver increases along a quadratic curve as the collapse progresses.